Lubricant compositions containing dithiocarbamates



United States Patent 3,412,026 LUBRICANT COMPOSITIONS CONTAINING DITHIOCARBAMATES Russell L. Booher, Edwardsville, Ill., asslgnor to Shell Oil Company, New York, N.Y., a corporation of Delaware No Drawing. Filed Dec. 12, 1966, Ser. No. 601,821 8 Claims. (Cl. 252-33.3)

ABSTRACT OF THE DISCLOSURE Oil compositions of outstanding oxidation stability are provided by incorporating therein a minor amount of an antimony dithiocarbamate and a hydroxybenzyl dithiocarbamate.

This invention relates to improved lubricating compositions having increased oxidation stability, and more particularly to lubricating compositions having good oxidation stability, even in the presence of relatively large amounts of pro-oxidant additives.

At one time straight mineral oils were able to meet all normal lubrication requirements of automotive and industrial practice. As these requirements became more severe with the progressive development of engines and machinery, it became necessary firstly to improve the quality of lubricating oils by new methods of refining and eventually to use additives to either reinforce existing qualities or to confer additional properties. These additives, e.g., dispersant polymers, pour depressants, viscosity index improvers, anti-wear and anti-rust inhibitors, etc., some of which contain metals, when added in large amounts to lubricating oil, act as catalysts or accelerators in promoting oxidation of the oil. These additives may appropriately be referred to as pro-oxidant additives. To further complicate the oxidation stability problem of lubricating oils, many of the oils are derived from crudes containing compounds which are readily attacked by oxygen, e.g., aromatics and olefins. Oil oxidation results in deterioration of the oil and formation of sludge deposits. Sludge is used to identify all types of engine deposits ranging from varnish-like films to baked carbon accumulations. Sludge causes engine wear, loss of lubrieating properties of the oil and generally loss of over-all engine efficiency. In the past, therefore, it has been necessary to establish a proper balance between oxidation inhibitor and, for example, detergent or dispersant in order to secure optimum oxidation resistance of the oil.

It has now been discovered in accordance with the present invention that lubricating oil compositions containing a minor amount each of antimony N,N-dialkyl dithiocarbamate and a dialkylhydroxy-benzyl N,N- diphenyl dithiocarbamate in solution therewith are inhibited against oxidation, even in the presence of pro-oxidant materials.

The above antimony N,N-dialkyl dithiocarbamate can be represented by the following formula:

wherein R is an alkyl radical having from 1 to carbon atoms, preferably from 4 to 6 carbon atoms. Both Rs may be either branchedor straight-chain alkyl radicals, for example, ethyl, i-propyl, s-butyl, t-butyl, n-butyl, namyl, n-hexyl, octyl, and the like. Preferred compounds of Formula (I) include antimony N,N-dibutyl dithiocarbamate, antimony N,N'diamyl dithiocarbamate and antimony N,N-dihexyl dithiocarbamate.

The dialkylhydroxybenzyl N,N diphenyl dithiocarbamate can be represented by the following formula:

wherein R is a branched-chain C alkyl radical and preferably t-butyl.

Base oils to which the dithiocarbamates described herein are added may be selected from a variety of mineral lubricating oils obtained from parafiinic, naphthenic, or mixed base crude oils, for example, neutral oils having viscosities ranging, e.g., from 60 SUS to 2000 SUS at F. Moreover, the oils may result from crudes which have or have not been highly refined. In addition to mineral lubricating oils, the carbamates may be added to synthetic lubricating oils such as polymerized olefins, silicone polymers, esters and ethers. Mixtures of natural and synthetic oils can also be employed.

Mineral lubricating oils which are particularly desirable for use in compositions of this invention are obtained from West Texas .Ellenburger crudes, East Texas crudes, Oklahoma crudes, California crudes. Useful refined oils therefrom include oils which have properties within the following ranges:

the following property ranges:

Gravity, API Min 24.5 Pour point, F. Max 5 Flash, COC, F. Min 415 Viscosity, SUS at 210 F. 58-63 Viscosity index 5060 The dithiocarbamate combination is particularly suitable for lubricating oil compositions which contain relatively large amounts of pro-oxidant additives or compositions which are less susceptible to inhibitors such as low viscosity oils prepared from crudes which are not highly refined. Thus, by using the combination of carbamates described herein, it is possible to formulate oil compositions which can contain relatively large amounts (up to 10% or higher) of numerous other additives such as corrosion inhibitors, pour point depressants, wear and corrosion inhibitors, viscosity index improvers, antifoaming agents, blooming agents, detergents, and the like and yet have a lubricating life equal to or greater than present lubricating compositions which contain only moderate amounts of these additives. The lubricating life of an oil is that period of time in which the oil is an effective lubricant for its intended purpose.

Specific examples of the pro-oxidant materials include (1) nitrogen-containing polymeric additives such as the copolymers of lauryl methacrylate and N-vinyl pyrrolidone; copolymers of lauryl methacrylate, stearyl methacrylate and 2-methyl-5-vinyl pyridine; an amide-imide of a mono C polymeric hydrocarbyl succinic anhydride, and the like, (2) basic additives such as, calcium salts of high molecular weight sulfonic acids, e.g., calcium naphtha sulfonates which are treated with calcium hydroxide to form the basic salts, and the carbonated calcium sulfonates, and (3) metal ions and acid-forming materials, as well as unsaturated organic compounds, but are not limited to these materials.

The amount of additive combination incorporated into the lubricating oil compositions may vary over a wide range, i.e., 0.01% to 20%, depending upon pro-oxidant materials present as well as the conditions under which the compositions are used. Ordinarily, the amount of additive combination present will be from 0.01% to by weight based upon the weight of the base oil, and preferably from about 0.1% to about 5%. Preferably, the zinc and antimony dialkyl dithiocarbamates are present in weight ratios of from 9:1 to 1:9, and most preferably from 7.5:2.5 to 25:75. Usually, the carbamates are present in equal weight ratios. However, beneficial coaction between the carbamates is obtained even when one of the carbamates is present in only trace amounts, although to a lesser degree.

The following examples are for purposes of illustrating the invention and are not intended to limit the invention to the particular compounds and compositions described. Unless otherwise specified, percent by wt. has reference to percent by weight based upon the weight of the base stock. In illustrating the invention, the following base stocks, compounds and compositions are referred to:

BASE STOCKS Base Stock A:

HVI 250 N (neutral) 228.4 SUS at 100 F.; 49.2

SUS at 210 F. Base Stock B:

20% spray base 60 HVI 250 N; 228.4 SUS at 100 F.; 49.2 SUS at 210 F.

10% LVI 65 N; 64.2 SUS at 100 F.; 34.9 SUS at 210 F.

4.5% of a mineral oil containing 36% by weight of a lauryl methacrylate/N-vinyl pyrrolidone c0- polymer (Acryloid 917).

5% carbonated calcium sulfonates.

Balance HVI 100 N; 95.3 SUS at 100 F.; 39.2 SUS at 210 F.

" HVI has reference to high viscosity index corresponding to S5 or higher.

1) A base oil having the following properties Gravity, API 30.4 Color, ASTM O.5 Pour point, F. 70 Flash, COC F 300 Viscosity SUS at F.

LVI has reference to low viscosity index corresponding to less than 40.

A solvent refined 150 SUS at 100 F. neutral oil,

COMPOUNDS The following compositions are prepared from Base Stock A and the above compounds.

COMPOSITIONS Composition. I.Base Stock A plus 0.5% by wt. of Compound a.

Composition II.-Base Stock A plus 1.0% by Wt. of Compound a.

Composition III.Base Stock A plus 0.5% by wt. of Compound g.

Composition IV.Base Stock A plus 0.5 by wt. of Compound d.

Composition V.Base Stock A plus 0.5% by wt. of Compound a plus 0.5% by wt. of Compound d.

Composition VI.-Base Stock A plus 0.5% by wt. of Compound 0. plus 0.5% by wt. of Compound g.

Composition VII.Base Stock A plus 0.5% by wt. of Compound f.

In order to illustrate the effectiveness of the carbamate combination to impart unexpected oxidation stability to lubricating oils, air oxidation tests were conducted. In these tests, a stream of air (30 ml./min.) was bubbled through a ZO-gram sample of lubricant (oil composition) in the presence of 20 p.p.m. each of copper and iron (as octoates) catalysts. The induction period, which is the length of time elapsed before a substantial increase in the rate of oxygen-uptake occurs, is a standard measure of oxidation stability and is tabulated below for each lubricant. In some instances the blotter spot life is also recorded.

These air oxidation tests were developed to simulate engine operating conditions under which sludge forms. The tests were conducted at 350 F.

OXIDATION TEST, RESULTS Lubricant: Induction period, hours Base Stock A 0 Composition I 4 Composition II 7 Composition III 3 Composition IV 3 Composition V 20 Composition VI 8 The above test results illustrate the effectiveness of the combination an antimony dithiocarbamate and a dialkylhydroxybenzyl diphenyl dithiocarbamate to impart oxidation stability to oils, whereas a combination of the diphenyl dithiocarbamate with a similar metal dialkyl dithiocarbamate, viz. zinc diamyl dithiocarbamate, or either of the individual carbamates per se is relatively ineffective. By reason of this effectiveness, it is possible to reduce the concentration of oxidation inhibitor presently required in lubricating formulations on the one hand or to improve other properties of the formulations on the other hand by maintaining the present oxidation inhibitor concentration while increasing the concentration of prooxidant additives.

Other additives may also be incorporated into the lubricating compositions according to the invention, for example, anti-foam agents, viscosity index improvers, rust inhibitors, and the like, as well as other anti-oxidants.

Compositions of this invention can be used as engine lubricants, hydraulic fluids, industrial lubricants, and the like.

I claim as my invention:

1. A lubricating oil composition comprising a major amount of lubricating oil and from 0.01% to about 10% each based upon the weight of the lubricating oil of (l) di-C -alkylhydroxybenzyl N,N diphenyl dithiocarbamate and (2) antimony di-C -alkyl dithiocarbamate.

2. A composition according to claim 1 wherein the oil is a mineral oil.

3. A composition according to claim 1 wherein the antimony dithiocarbamate is antimony diamyl dithiocarbamate. V

5 4. A composition according to claim 3 wherein the N,N-dipheny1 dithiocarbamate is 3,5-di-t-butyl-4-hydroxybenzyl N,N-diphenyl dithiocarbamate.

5. A lubricating oil composition comprising a major amount of lubricating oil, a minor amount of pro-oxidant 5 material, and from 0.01% to about 10% each by weight based upon the weight of the lubricating oil of (1) di- C -alkylhydroxybenzyl N,N-diphenyl dithiocarbamate and (2) antimony di-C -alkyl dithiocarbamate.

6. A composition according to claim 5 wherein the prooxidant material includes a lauryl methacrylate/N-vinyl 1O 3260758 group consisting of a basic calcium salt of a high molecular weight sulfonic acid, a lauryl methacrylate/N- vinyl pyrrolidone polymer and a combination thereof.

References Cited UNITED STATES PATENTS 3,081,335 3/1963 Morris et a1. 260-455 3,117,947 1/1964 Turner 260 455 3,239,462 3/1966 Bergstrom et a1 252-33.6

7/1966 OShea et a1. 260455 FOREIGN PATENTS 984,413 2/1965 Great Britain.

15 DANIEL E. WYMAN, Primary Examiner.

W. H. CANNON, Assistant Examiner. 

